1. Field of the Invention
The present invention relates to a camera system including an electronic flash device with a slave emission function.
2. Related Background Art
Conventionally, an adapter, called a wireless multiple-flash adapter or a slave unit, for wireless-controlling an electronic flash device to emit light is available. In this adapter, upon reception of a steep change in light by a light-receiving element, a switching element is turned on in response to this light, and a synchronous signal is output to control an electronic flash device connected to the adapter to emit light. Therefore, in a multiple-flash photographing operation using a plurality of electronic flash devices for illumination, the adapter and the electronic flash devices can be conveniently disposed at arbitrary positions. As the adapter, a stand-alone adapter and an adapter built in an electronic flash device are available. As an example of an adapter built in an electronic flash device, in Japanese Laid-Open Utility Model Application No. 56-3527, a light-receiving element for slave emission is disposed in the same direction as the optical axis of a light-emitting portion. On the other hand, as described in Japanese Laid-Open Patent Application No. 55-153927, a device which has a delay circuit inserted between a photosensitive element and a switching element is also proposed.
However, in the above-mentioned prior art, the slave unit operates as an independent unit. For this reason, when various TTL light control modes are executed via various data communications with a camera as with the recent trend, many problems are posed. In a so-called delayed emission mode for performing slave emission after an elapse of a delay time from master emission, the synchronous time must be delayed in advance. In such a situation, a photographer must perform a manual operation (e.g., must delay the shutter speed), and a photographing failure often occurs due to, e.g., a setting error. Furthermore, in a rear synchronous photographing operation, since a master unit starts light emission immediately before the rear curtain of the shutter begins to travel, the delayed emission by a slave unit inevitably causes a synchronization error. In this situation, selection can only be made between two alternatives, i.e., inhibition of the rear synchronous photographing operation or inhibition of the delayed slave emission operation.